Sulphurised calcium alkyl phenate detergents are well known additive components for internal combustion engine crankcase lubricating oil compositions. However, certain alkylphenol sources (nonylphenol, tetrapropenylphenol) used in their manufacture are classified as reproductive toxins; accordingly, there is a desire to identify other phenol sources.
The art describes a way of meeting this problem. Thus, U.S. Pat. No. 5,910,468 ('468) describes the preparation of sulphurised calcium alkyl phenate from, as the phenol source, distilled or hydrogenated-distilled cashew nut shell liquid (CNSL). Distilled CNSL is a mixture of biodegradable meta-hydrocarbyl substituted phenols, where the hydrocarbyl group is linear and unsaturated, including cardanol. Catalytic hydrogenation of distilled CNSL gives rise to a mixture of meta-hydrocarbyl substituted phenols, predominantly rich in 3-pentadecylphenol.
A problem with the process described in '468 is that the sulphurised calcium alkyl phenate detergents thereby produced lack satisfactory deposit control performance.